-LRB- CNN -RRB- -- Civilians are in hiding in the Yemeni capital as protesters and government forces struggle for control on the streets of Sanaa .

Residents in Sanaa are stranded in their homes , and some even fear looking out of their windows as they are left to wonder how long the violence will rage around them .

`` We ca n't leave our houses to get food for our children . As soon as we walk on the street we are shot , '' says Rami al-Shaibani , a Sanaa resident .

Thousands protested in Sanaa 's Change Square last week , but this week the square has been quiet , except for groups of youths carrying away the dead and helping the injured . Multiple witnesses and medics said dozens were killed in a violent government crackdown that started on Sunday .

Protesters have used Change Square for a seven-month sit-in demanding the resignation of President Ali Abdullah Saleh . He is recuperating in Saudi Arabia from a attack in June on his palace but has vowed to return to Yemen to finish his term .

Each wounded protester was carried by six or seven others -- sometimes friends of the casualty -- and taken to the medical camp in the square . Drops of blood created trails on the ground tracing the long , bloody route to a field hospital .

At the medical camp , hundreds of young people were covered in blood and screaming from pain . Thousands more volunteered and donated blood for those in need . It seemed that not a minute passed without another injured youth entering the medical camp .

The International Committee of the Red Cross has called for calm in Yemen , which , it said , is facing an `` unprecedented level of violence . ''

With the limited-capacity field hospital full of patients , doctors made a desperate call for volunteers to try to help save the injured .

Dozens were killed and more than 700 were wounded -- many of them by gunshots -- over the last three days in clashes with the military , according to medical staff in Change Square .

Eyewitnesses said they had seen snipers on the rooftops of buildings surrounding the square firing almost continuously .

In one incident , an ambulance carrying three injured protesters flipped over when a rocket propelled grenade hit it , killing all five on board , the medical staff added .

Abdul Rahman Barman , the executive director of a local human rights organization , said Yemeni President Ali Abdullah Saleh 's regime is attacking with no limits and does not differentiate between civilians , protesters or gunmen .

The Yemeni government has repeatedly denied accusations of excessive use of force , and said the government is committed to establishing a peaceful transfer of power . Yemeni officials have said forces cracked down on those committing acts of violence during protests . Vice President Abdu Rabu Hadi has called for a cease-fire from all sides , state-run Saba news agency reported .

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Dozens in capital Sanaa have been killed in a government crackdown since Sunday

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The Red Cross says Yemen is facing an `` unprecedented level of violence ''

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Eyewitnesses say they saw snipers firing on crowds in Sanaa 's Change Square